1. Field of the Invention
This invention relates to a copying apparatus and more in particular to a multiple reproduction apparatus which is capable of varying the wait time of an original holder or optical system at its home position in accordance with the size of originals or copy papers.
2. Description of the Prior Art
A copying machine capable of making multiple copies in succession is well known. In general, a copying machine includes an original holder for holding an original thereon, a photosensitive member for forming thereon an electrostatic latent image of the original and an optical system for leading the light image of the original to the photosensitive member. In actual machines, the photosensitive member is usually in the form of a drum which is rotatably supported by a machine housing. Such a photosensitive drum is driven to rotate in synchronism with the scanning of the original.
When scanning the original, either the original holder or the optical system must be moved with respect to the other in a reciprocating manner. For example, in carrying out scanning in the system where the original holder moves with respect to the stationary optical system, the original holder advances from its home position to a certain forward position and upon reaching the forward position, the original holder returns to the home position. In making multiple copies from the same original, the original holder stays still for a predetermined period of time and then it again executes its reciprocating movement. Such a wait time at the home position in a multiple reproduction is necessary in order to obtain proper synchronism among associated components. The above also holds true for the system where the original holder is stationary and the optical system is movable with respect to the original holder.
In accordance with prior art copying machines capable of making multiple copies in succession, the wait time of the original holder or optical system at the home position is constant. Therefore, the original holder or optical system, whichever is movable, stays still temporarily for a predtermined period of time at the home position every time when the original holder or optical system returns to the home position in a repetitive copying operation. Thus, in the case where the forward position is varingly determined in accordance with the size of copy papers to be used, the number of copies per unit time is uniquely determined by the copy paper size. For example, if a prior art copying machine has a rated performance of making 28 A4-sized copies per minute, the numbers of copies per minute for differently-sized copies such as A3 and B4 are individually determined according to their sizes.
Therefore, in prior art copying machines, it is not possible to set the number of copies per unit time to an appropriate value. Prior art copying machines having a constant wait time at the home position are particularly disadvantageous in that toner-image fixing performance tends to degrade as use is made of larger-sized copy papers. Such degradation could become worse for modern copying machines in which use is made of an energy-saving type fixing device having a relatively low thermal capacity. That is, if the larger-sized copies are processed with the same time interval between copies as the smaller-sized copies in such a condition, sufficient fixing may not be obtained for the larger-sized copies.